// sidebar 
var $ = function (selector) {
    var NodeList = document.querySelectorAll(selector)
    return Array.prototype.slice.call(NodeList, 0)
}
var $content = $('.content iframe')[0];
// 点击左侧菜单，改变右侧内容
$('.sidebar li').forEach(item => {    
    item.addEventListener('click', e => {
        var url = e.target.dataset.url;
        var oldUrl = $content.src
        if (!oldUrl.includes(url)) {
            $content.src = url
        }
    })
})